The purpose of this field project is to evaluate the impact of a combined water-sanitation intervention on the occurrence of pediatric diarrhea and other targeted outcomes in a study population residing in the Assiut governorate of Upper Egypt. 20 villages, which together included a population of approximately 10,000 persons, were randomly assigned to receive the intervention (N=10) or no intervention (N=10). The intervention consisted of provision of India Mark II tubewells and household latrines, together with an educational package stressing personal hygiene and water behaviors. To assess the impact of the intervention, all families in these villages were followed with longitudinal surveillance during a one-year follow-up period. Although the baseline incidence of diarrheal episodes (per 1000 person-days of follow-up) in children under three years of age was similar in intervention (29) and control (29) communities, after zero-time rates of diarrhea decreased 17% (p less than .0001) in the intervention relative to the control communities. Protective associations were slightly higher for blood diarrhea (25%, p less than .05) and persistent diarrhea (26%, p less than .0001), suggesting that the intervention might have reduced not only the risk of diarrhea but also the severity of diarrhea. In contrast, no impact on the occurrence of respiratory infections was evident, indicating that the decline of diarrhea in the intervention communities was not likely to be due to ascertainment bias. It was of particular interest that intervention communities exhibited a marked increase of per capita water consumption, but that the new pumps continued to produce water that was contaminated by fecal coliforms. There data suggest that the salutary effect of the intervention may have been mediated, in part, by increased water consumption, though the water itself was fecally contaminated. Analyses will continue in FY94.